1. Field of the Invention
The present invention relates to adsorbents for removing HCl from fluid streams. More particularly, the present invention relates to a promoted alumina adsorbent for removing HCl from fluid streams.
2. Description of the Background
HCl is present as an impurity in numerous industrial fluids, i.e. liquid and gas streams. For example, in reforming processes conducted in refineries, a chlorine promoted catalyst is generally employed. During the reforming operation, which also generates hydrogen, small amounts of gaseous HCl are produced which is carried away with the hydrogen. The hydrogen containing the HCl is generally recycled to the reformer. Accordingly, the small amounts of gaseous HCl present in the recycle hydrogen can seriously interfere with the operation of the process and, in addition, can cause corrosion problems. Additionally, there are other processes in which small amounts of HCl are generated and carried away in gas or liquid streams and which must be removed from such streams to prevent corrosion damage to equipment and avoid environmental problems.
It is well known that activated alumina can act as a scavenger for the removal of small quantities of HCl from fluid streams. For example, U.S. Pat. Nos. 4,639,259 and 4,762,537 both disclose alumina based adsorbents for removing HCl from gas streams. Typically, HCl scavengers made from alumina are formed into nodules, e.g., spheres, the spheres forming a fixed bed through which the gas to be scavenged flows. Handling and use of the nodules dictates that they possess sufficient crush strength to retain structural integrity. It is also known that aluminas impregnated with up to 5% sodium carbonate or sodium hydroxide exhibit improved performance in terms of enhanced hydrogen chloride absorption capacity. This is especially desirable since it means that the user can enjoy longer run times before having to change out the adsorbent, or in the case of new units can design the units smaller. By increasing the content of promoters such as sodium carbonate, or sodium hydroxide, the HCl adsorbing capacity of the scavenger can be increased. However, heretofore, attempts to increase the content of such promoters has resulted in a scavenger which does not possess sufficient structural integrity to be useful in commercial applications.